1. Field of the Invention
The present invention relates to a display apparatus having a function of inputting information via an optical sensor.
2. Description of the Related Art
Conventionally, a mouse or a keyboard is used in order to supply an input signal to a computer. Also, a remote control is used for a user to select a specific function in a digital television (TV). However, a user may have difficulties using input devices, such as a mouse, a keyboard, or a remote control if he is not accustomed to handling them.
Touch panels or touch screens are innovative input devices that are developed to remove such difficulties. The touch panels allow a user to input a command signal by directly touching a display panel with the user's finger or a pen rather than by using, for example, a mouse. Accordingly, users who have difficulty with using an input device, such as a mouse or a keyboard, may use a digital apparatus such as a computer without difficulties simply by directly touching a display panel with, for example, his/her finger. Touch panels may be categorized according to a method of sensing an external input. For example, the touch panels may be categorized into those using electrostatic capacitance, those using a resistive layer, those using ultrasonic waves, those using an integral method of measuring tension, those using the piezo effect, and those using optical sensing.
In particular, in touch panels using optical sensing, contact made by, for example, a user's finger is sensed by forming a photo diode in a panel and sensing current generated by light that is incident on the photo diode. The photo diode that is an element essential to such touch panels is simple to manufacture since it can be manufactured in a process of forming a driving circuit of a display panel, such as a liquid crystal display (LCD) or an organic light emitting diode (OLED).
However, with a conventional method of sensing light, it is difficult to determine whether or not an object, such as a user's finger or a light pen, touches a screen and to precisely calculate the coordinates of the object. Also, with the conventional method, is disadvantageous in that erroneous sensing may be caused by a shadow of an object and a large amount of power may be consumed by a light sensor scanning circuit operating regardless of whether or not contact is made by a specific object and a circuit for reading out a signal sensed.